In the manufacture of printed circuit boards in the electronics industry there is a need for an ink for marking printed circuit boards and electronic components which will not be removed by the solvent baths and vapor degreasers used to clean the completed printed circuit boards in the final stages of manufacture. At the present time the only inks which do this are (1) Thermosetting inks or (2) Epoxy inks.
The thermosetting inks are satisfactory for individual components which are designed to stand the baking temperatures but not for marking on assembled printed circuit boards where there are also components which will not stand the baking temperatures. The epoxy inks must be mixed at the time of use and have a pot life usually of less than one hour. They also require periods of more than an hour to harden to the point the printed circuit boards may be handled without smearing the ink. Epoxy inks also do not stand extended solvent vapor degreaser action with good predictability. They may come off some surfaces and stick on others. It is desirable also that there be a method of removing the ink without destroying other markings on the component or printed circuit boards.
In hospitals and chemical laboratories there is a need for an ink for bottles and specimens which will not be attacked or dissolved by organic solvents in the bottles or used in processing.